Fuel igniter



J. G. COHN FUEL IGNITER Filed NOV. 26, 1948 Nom 8, 1949 INVENTOR.

JOHANN @UNT'HER CQHN BY// AM( A TTQQNEY Patented Nov. 8, 1949 NITEDSTATES PATENT ()l;"I*`,ICI:

FUEL IGNITER Johann Gunther Cohn, East Orange, N. J., assignortoBaker-@r Co., 1nc.Newark,-KN.VJ., acorporation kof New JerseyApplicationNovember 26, 1948, SerialfNo. 62,190

(Cl. 21S- 32) .3 .Claims .Il

The Ipresent invention KVdeals with the .ignition of .fuels and isconcerned'more particularly with the provision of an automatic igniteryfor fuels, such asorganic `inflammable gases, .in nelydivided state.

Efforts have been made :for many years .torreplace-fthe open-.flame gaspilot light by more economic` and-safermeans. Electricignition by meansofan electrically heated Aincandenscent w-ireor the like brought -to theignition temperature of the rfuelis, of course, superior to fthe openpilot light .insofar as safety is concerned, but other-Wise,onlysubstitutewaste of electrical energy for waste of fuel energyand, furthermore, requiresan expensive mechanism.

vIn my co-pending applications, No.;792,67.3 and No.792,6f7.4, Iihavedescribed automatic igniters in .the :formof acatalyst of ne .diameter.Wire in the shape ofa coil electricallyheatedtoa temperaturesubstantially below the ignition temperature of the fueLVthecOil of theigniterof application No. r792,674 being more particularlyso constructedas zto constitutea heterophase .catalyst wherein .thacatalyticreactionstarts at lone phase andignitionoccurs at anotherphase. -Such electrically heated catalytic igniter constitutes Lathe rstpractical vautomatic :igniter capable of reliably igniting, on contact,finely divided fuels .irl ailowingffuel-.airmixture in which the fuelcomprises inammable materials difficult to ignite, such as suchsaturatedhydrocarbon gases as butane, propane, or even methane, or thelike.

The present invention deals more specifically with a furtherimprovementupon the automatic igniter of my present co-pendingapplications above referred to.

T hechief object of this invention is to provide an automatic catalytic'igniter which shall be highly superior in its function and efficiencyin the ignitionof fuels most difficult to ignite, such as naturalgas andin particular a gas as difficult to ignite catalytically as methane, andwhich, in this function and itseiiiciency, is even superior to theigniters shown more specifically inmy co-pending application-No.792,674. It is another object of this inventiony to provide such igniterforsuch flowing fuel-air mixtures comprising saturated gaseoushydrocarbons or. other finely divided organic yfuels whereinsuch,mixtures may be substantially devoid of free hydrogen or wherein atleast the free hydrogen, ifany, is practically ineffective in the-ignition process. vIt is another object to providea highly-efficientautomatic igniter, of the catalytic type, suitable for the safe andreliable .ignition .of vany and all fuel-air mixtures containinginammable .constituents adapted to be catalyzed. It is a furtherobjectof the invention toprovide such igniter which-shall operatereliably overa widerange of fuel-air com.- positions. It is anothervobject of this invention to provide an .automatic .igniter .which.shall `be easyfand simpleto manufacture. AOtherobjects and :advantagesof the Vautomatic; ,fuel :igniterrof my invention vwill appear .from the:description thereof hereinafter following.

As in my.co-pending.applications referred to, the catalyst wire-of theigniter mustnavea very small diameterand be shaped toform a coil. Thewireconsists, or has atileast a surface, of catalyst metal adaptedtocatalyze the fuel in the-fuelfair mixture :in a flameless combustion,the catalyst comprising suchmetal as platinum or .othermeta-l of.theplatinum group or alloy thereof. The coil is electrically heated toa Itemperature substantiallygbelowthe ignitiontemperature ofthe finelydivided fuel, .such as methane or other saturated hydrocarbon gas, inthe fuel-air mixture.

The specific ,feature 0f theigniterpffths vinventionis thatzthe @Oiled.Wire .iS-.inftwn Shared yinto a coiled or fothersuitable .structurei.ve. a Iprimary @.011 Qf nefcoil. diameter is formed, e. s. intoasecondary coilvof larger coil diameter, as -for Ain- Stance a lfcoiled0011- AReference Vvis .made t0 kthe drawings, forming partnered, inwhich:

Figure I-:repreSeHtS a diagram@ an ieniien System embodying the igniter.

Figure 2 r.represents an enlarged ,elevational View, Shownfschematcally,of the'igniter Of'ths invention, .and

.Figures 3 anderepresentglike views Qf Av10.deiil embodiments of theigniter.

.Referring :Imre partularlv @Figure .1, .the igniter I,illustratedschematically,only, is shown within a: Aclua1;1@.-Shfbacksystem. YThe burners to be lit, areindicated ati/2 and 2. Agaseousmixtureflowing fromme@ .aSh-back ports 3 and 3', enters thetWQaSh-.backtubeS'f-i f5 andoWS towardand into contact with theignitler l where it is,;on contact, ignited. {I he'flamethen travels iniiash-back manner backto, the flash-back ports 3 and 3 and there establishescontinuouslyburning arnesbywhich ,the gas flowing throughthe burners ,2and 2 becomes ignited. 'While inthis Figure 1, Ihave illustratedaZ-burner unit, vit will be understood that the same principleapplies tothe ignition of othermultiple burner, units ora single burnerlunit.

nReferring now more particularly Yto Figures .-2,

. .3 and fi, the igniter itself consistsof Ya4 coiled wire 5 of catalystmetal, e. g. platinum or metal of the platinum group or alloy thereof,shaped into a secondary form comprising a twisted structure of variatedform. In Figure 2, the structure is shown as a coiled coil with aplurality of turns and in Figure 3 as a plurality of V-bends and inFigure 4 as a plurality of simple bends forming at least one S-shapedstructure. The structures shown in Figures 2-4 are intended asillustrations, other twisted shapes and structures of the ne coiled wirebeing possible, such, e. g. as a simple loop.

The coiled coil in which a densely wound primary coil of small diameteris wound into the shape of a secondary coil having turns of largerdiameter, relative to the diameter of the turns of the primary coil, andother such twisted structures, as shown, are of the nature of aheterophase catalyst in which the catalytic reaction starts at one phaseand is accelerated to ignition at another phase activated by the phaseat which the reaction starts.

The wire itself of the igniter must have a very flne diameter, of theorder of a minimum of about 0.001", and a maximum of about 0.003". Theprimary coil may have an inner diameter of from about 0.002 to about0.015 and a spacing of from about 50 to about 400 turns per lineal inch.The secondary coil, or winding, may have an inner diameter of from about0.01 to about 0.1". For example, when a Wire of 0.001" or 0.002" isused, the primary coil may consist of a great number of close turns, e.g. of the order of 135 turns per lineal inch, the turns having an innerdiameter of 0.005", whereas the secondary coil, of at least two or moreturns, has an inner diameter of about 0.035. The igniter structure iselectrically heated, by resistance, to a temperature well below theignition temperature of the flowing fuel-air mixture and, of course,below the recrystallization temperature of the metal of the structure.Such heating is accomplished with extremely small current of low voltageand low amperage. On contact with the flowing fuel-air mixture, thereaction starts immediately and is almost instantaneously accelerated toignition with an attendant increase of the temperature of the igniter,whereupon the burning gas is removed from contact with the igniter, asfor instance by means of the flash-back system or f otherwise. Thesource oi electric power is indicated at 6, which may be either abattery or a transformer, with leads 'l and 'I'. The electrical heatingmay be continuous, or it may be controlled to coincide with theoperation of the burner unit or units so as to occur only on opening ofgas jets.

The igniter of this invention represents an extremely efcient device forthe ignition of flowing fuel-air mixtures, even those wherein the fuelis such diiicultly ignitable a fuel as methane.

'I'he igniter of the present invention is superior in reliability ofignition to any other structural form of electrically heated catalyticigniter. In my co-pending application No. 792,674, I have more fullyexplained the heterophase principle of the catalytic igniter in that thecatalytic reaction starts at one phase, the primary phase portion, whichin turn heats up fast the secondary phase portion at which thereupon thenameless reaction at the primary phase portion is accelerated to flameformation and ignition. In the instant case, the igniter operateslikewise on this heterophase principle. In the formation of thesecondary coil or the like, the initially even and uniform 4 spacingbetween the turns of the coil is changed to an uneven spacing, the innerparts of the primary turns coming closer together and the outer partsspreading apart, resulting, thus, in a greatly variated structure inwhich numerous sections of closely spaced turns are adapted to act asprimary phases alternating with numerous sections adapted to act assecondary phases, thus affording to the impinging fuel-air mixture alarge number of starting points, primary phase, for the reaction andadjacent areas, secondary phase, Where the initial reaction can beaccelerated to ignition.

Even a mere bend, or loop, of the fine-diameter coil creates anefficient automatic igniter, although the preferred form of igniter inaccordance with this invention is one in which the primary coil isshaped into a large-diameter coil or other structural forms having aplurality of primary and secondary phases.

The superiority of the igniter of this invention over other electricallyheated catalytic igniters and over other types of such heterophaseigniters is evidenced by its performance.

For instance, a 0.002 wire wound into a primary coil having an insidediameter of 0.005, 135 turns to the lineal inch, and then Wound into asecondary coil of two or three turns and having an inside diameter ofabout 0.035" invariably ignited methane in a flowing methane-air mixtureon heating with from about 0.25 watt to about 0.6 watt with a voltage offrom 1.30 volts, and 0.2 ampere, to 2.5 volts and 0.225 ampere. Astraight single coil would be unable to ignite methane under any such orsimilar conditions.

A similar igniter in the form of the twisted structure of Figure 3 or ofFigure 4 operates in like manner. For instance, such igniter of 0.002"

wire coiled into a primary coil having an insider diameter of 0.004, 135turns to the lineal inch,

i and shaped into the W-structure of Figure 3 and heated with 0.5 watt,or 1.9 volts and .26 ampere, ignited methane in the above-mentionedmethane-air mixture instantaneously. The S-structure of Figure 4requires for like performance a slightly higher power, e. g. 0.55 wattfor a wire coil as above stated, or 0.29 ampere and 1.9 volts.

The number of turns of the secondary coilmay vary, there being at leasttwo such turns. Normally, it is safest to employ three or four turns andif desired, there may be more such turns of the secondary coil. Thevoltage and the amperage of the electric heating current, and the totalwattage input, must be sufficiently small, correlated to the wirediameter, to maintain the temperature of the coil at the specified lowtemperature. Generally speaking, the igniter of my invention will notglow when not in contact with the owing fuel-air mixture, although aslight glow may occur in some cases.

The catalyst metal of which the wire, or at least the surface of thewire, is formed, is usuallyplatinum or an alloy of platinum with anothermetal of the platinum group, e. g. such alloys of platinum and rhodiumor platinum and iridium,

the platinum content normally being at least or of the alloy, 0r Withother suitable metal or metals, such for example as nickel, tungsten,and so forth. The wire material may be in the form of a sinteredagglomerate of the catalyst metal or metals, with or without othermetals, e. g. tungsten, and, preferably, with a small percentage, orfraction of a percent, of refractory oxide distributed therethrough,such as thorium oxide, beryllium oxide and so forth. The wire may haveany desired cross-sectional shape,

usually,v however, circular. Stranded wire. may also be used in theformation of the structural igniter of this invention, in which case theoverall thickness of the wire composed of the individual strands shouldcorrespond in electrical resistance to that of the wire herein describedotherwise; in this case, the individual strands need not necessarily becomposed of the same metal but may consist of dilerent metals orcompositions.

Experiments with the igniter of this invention have shown, further, thatit is far superior to other igniters even in the ignition of city gas,i. eso-called manufactured gas, which contains a certain amount ofhydrogen. In general, in the ignition of such gas, the power input hasbeen found to be about less for ignition by means of the igniter of thisinvention compared with an otherwise similar simple straight coil, forobtaining ignition. However, the most significant difference is foundwhen the igniter is used for the ignition of such gas in multipleburnerunit, since in such arrangement, see e. g. Figure l, the combustionproducts flowing from one ignited flash port, e. g. 3, through flashtube 4 and impinging on the igniter I, mingle with the gas stream to beignited which is flowing from flash port 3 through flash tube 4', andtend to blanket the igniter and interfere with the second ignition. Asingle straight coil is apt to become unreliable, or slower in itsignition action than a coil according to the present invention. The fargreater reliability of the present igniter when used to light two ormore burners, either together or in succession, is of the greatestimportance in assuring maximum safety.

The fuel-air mixtures in the experiments described resulted from a jetof fuel, e. g. methane, through nozzles, into air, and are thus thecustomary mixtures encountered in practical systems such as gas rangeburners. The flames were of the characteristic blue color. The pressureof the jet varied over wide ranges as encountered in heating practice.

The manner of connecting the igniter to the source of electric power maybe conventional. In Figure 1 I have shown one particularly suitablemethod of mounting the igniter and connecting it to the electric power.Lead-in wire 'I' is connected to a metal sleeve 8 mounted on aninsulated base 9, and lead-in wire 1 i-s connected to a contact I0, inthe form of a sleeve, mounted within the base 9 and electricallyinsulated against the metal sleeve 8. The igniter I is mounted betweenthe two leads II and II', which simultaneously serve as supports andwhich are mounted on a cap I2, lead-in II being soldered to or otherwisebeing in metallic contact with the cap I2 and lead-in II being isolatedfrom the cap by means of a sleeve I3 terminating in a metallic tubularextension I4. The cap I2 is pressed down onto and over the sleeve 8,thus bringing the lead-in I I in contact with the conductor I and thelead-in II in contact with the contact sleeve I0 and thereby withconductor l, the entire assembly being held together by the frictional tof cap I2 over sleeve 8 and of the tube i4 within the sleeve I0.

The igniter may be used in domestic and industrial appliances, such asranges, stoves, furnaces and so forth, whether direct, as e. g. in topburners of ranges, or indirect, as e. g. in range ovens or furnaces. Itmay also be used in instruments or other devices Wherever it is desiredto ignite a gas-air or other fuel-air mixture. The source of electricpower may be the line supply, with an interposed resistor or suitabletransformer, or a battery, as may be desired. The electrical heating ofthe igniter may be continuous or limited to coincide with the presence,

of the air-fuel mixture at the time ignition is desired. As in mypreceding applications, above referred to, the fuel-air mixture iswithdrawn from contact with the igniter after ignition has occurred, ase. g. by means of the flash-back system. The igniter may also be usedfor the ignition of a gas which in turn is used for the ignition ofanother fuel which by itself is either too difcult to ignite or in whichignition is too unreliable.

What I` claim is l. An automatic igniter for organic fuels in nelydivided state capable of being catalytically oxidized in a flowingfuel-air mixture in the presence of a catalyst, comprising anelectrically heated heterophase catalyst having at least a primary phaseportion to initiate the catalytic oxidation and a secondary phaseportion to be activated by the heat of the reaction at the primary phaseportion and thereupon to complete the catalytic oxidation to the statewhere the flameless combustion of the catalytic oxidation is convertedinto flame combustion, the said catalyst consisting of a closely spacedhelical coil of catalyst metal, the wire of said coil having a diameternot in excess of about 0.003", said coil being in turn formed into acoil having a plurality of turns, a source of electrical power connectedto said coil to heat said coil to a temperature substantially below theignition temperature of said fuel in said fuelair mixture and below therecrystallization temperature of said catalyst metal, and means forterminating the contact between the catalyst and the ignited fuel.

2. An automatic igniter for organic fuels in finely divided statecapable of being catalytically oxidized in a fuel-air mixture in thepresence of a catalyst, comprising an electrically heated heterophasecatalyst taken from the group of metals of the platinum group and alloysthereof, having at least a primary phase portion to initiate thecatalytic oxidation and a, secondary phase portion to be activated bythe heat of the reaction at the primary phase portion and thereupon tocomplete the catalytic oxidation to the state where the flamelesscombustion of the catalytic oxidation is converted into flamecombustion, the said catalyst consisting of a closely spaced helicalcoil of said catalyst metal, the wire of said coil having a diameter notin excess of about 0.003, said coil having an inner diameter of fromabout 0.002 to about 0.015 and a coil spacing of from about 50 to 400turns per inch, said coil being in turn formed into a larger coil havingan inner diameter of from about 0.01 to about 0.1, a source ofelectrical power connected to said coil to heat said coil to atemperature substantially below the ignition temperature of said fuel insaid fuel-air mixture and below the recrystallization temperature ofsaid catalyst metal, and means for terminating the contact between thecatalyst and the ignited fuel.

3. An automatic igniter element for organic fuel in finely divided statecapable of being catalytically oxidized in a flowing fuel-air mixture inthe presence of a catalyst, comprising a catalyst consisting of aclosely spaced helical coil of metal taken from the group of metals ofthe platinum group and alloys thereof, the Wire of said coil having adiameter not in excess of about 0.003,

7 saidV coil being in turn formed into a coil having a, plurality ofturns, a mounting for said catalyst and including lead Wires to oppositeends of said coil for connection to a source of electrical power of suchorder of magnitude as to heat said coil to a temperature substantiallybelow the ignition temperature of said fuel in said fuel-air mixture andbelow the recrystallization temperature of said catalyst metal.

JOHANN GNTHER COHN.

REFERENCES CITED The following references are of record in the fue ofthis patent:

UNITED STATES PATENTS Name Date Van Hoevenbergh Sept. 15, '1896 NumberNumber Number

